C - sockets - connect:result too large (windows) - c

Question

I've been a Unix programmer for a decent amount of time, and I know pretty well the system's socket API, I use it mostly for networking.
The thing is that I'm currently trying to create a cross-platform software, and so I began to learn how to compile my source code into windows executable files.
I've created a startup() function which does the simplest thing: connect to a server (of which IP is given), and return -1 on failure. On Linux my code runs smooth, but on Windows(7) I get the same error on some machines - "Connect()" function failed, errno: "Result too large" which (by what I understood) means it could no find any listening server on that IP, but on others it runs well.
Here is the code (win version):
#define _WIN32_WINNT 0x0501
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <windows.h>
#include <winsock.h>
#define ADDR "127.127.127.127"
#define PORT 8752
int startup(struct sockaddr_in sin)
{
int sockfd, soaddr;
WSADATA wsaData;
if (WSAStartup(MAKEWORD(1,1), &wsaData) != 0) {
fprintf(stderr, "WSAStartup failed.\n");
exit(1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
{
fprintf(stderr, "socket:%s\n", strerror(errno));
return(-1);
}
soaddr = sizeof(sin);
if(connect(sockfd, (struct sockaddr*)&sin, soaddr) == -1)
{
fprintf(stderr, "connect:%s\n", strerror(errno));
return(-1);
}
return sockfd;
}
int main(int argc, char *argv[])
{
int sockfd;
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(PORT);
sin.sin_addr.s_addr = inet_addr(ADDR);
sockfd = startup(sin);
// Code continues
return(0);
}
note:ADDR has been changed for privacy reasons, but there is a working server on that machine
So, why exactly am I getting this error ?

Answer 1

WinSock does not use errno, it uses WSAGetLastError() instead.
WinSock does not use file descriptors for sockets, it uses actual kernel objects. On Windows, you need to use the SOCKET handle type, not int, for your socket variables (or at least type-cast SOCKET values to (u)intptr_t and then type-cast back to SOCKET when calling WinSock functions).
You can use the Win32 API FormatMessage() function to get a human readable string for a WinSock error code.
#define _WIN32_WINNT 0x0501
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <windows.h>
#include <winsock.h>
#define ADDR "127.127.127.127"
#define PORT 8752
__declspec(thread) char errmsg[256];
char* sockerr(int errcode)
{
DWORD len = FormatMessageA(FORMAT_MESSAGE_ARGUMENT_ARRAY | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, errcode, 0, errmsg, 255, NULL);
if (len != 0)
errmsg[len] = 0;
else
sprintf(errmsg, "error %d", errcode);
return errmsg;
}
int startup()
{
WSADATA wsaData;
int ret = WSAStartup(MAKEWORD(1,1), &wsaData);
if (ret != 0) {
fprintf(stderr, "WSAStartup:%s\n", sockerr(ret));
return(ret);
}
return(0);
}
void cleanup()
{
WSACleanup();
}
SOCKET connectToServer(struct sockaddr_in sin)
{
SOCKET sockfd;
int soaddr;
sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sockfd == INVALID_SOCKET)
{
fprintf(stderr, "socket:%s\n", sockerr(WSAGetLastError()));
return(INVALID_SOCKET);
}
soaddr = sizeof(sin);
if (connect(sockfd, (struct sockaddr*)&sin, soaddr) == -1)
{
fprintf(stderr, "connect:%s\n", sockerr(WSAGetLastError()));
closesocket(sockfd);
return(INVALID_SOCKET);
}
return(sockfd);
}
int main(int argc, char *argv[])
{
SOCKET sockfd;
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(PORT);
sin.sin_addr.s_addr = inet_addr(ADDR);
if (startup() != 0) {
exit(1);
}
sockfd = connectToServer(sin);
if (sockfd != INVALID_SOCKET)
{
// ...
closesocket(sockfd);
}
cleanup();
return(0);
}
You will have to take these differences into consideration when writing cross-platform socket code.

Answer 2

According to your code you are running client socket in windows machine.You need to load runtime libraries for windows as
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")
You can refer to Windows Client Socket Source. Hope this works for you.